More momentum —

Seagate makes momentous move to expand and rebrand

We reported yesterday that Seagate is discontinuing its 2.5-inch 7200 RPM consumer hard disk drives, leaving an apparent hole in its consumer drive lineup between value-oriented 5400rpm HDDs and its faster Momentus XT hybrid disks (which incorporate NAND flash as a disk cache). The reasoning for that discontinuation has become clear this morning, as Seagate is expanding its hybrid drive offerings to fill as many of the holes as it possibly can.

Gone is the "Momentus XT" brand, which used to denote Seagate's hybrid hard drive + NAND disks—the new name for the entire hybrid line is "Solid State Hybrid Drives," or SSHDs.

The rebranding change affects not just the 2.5-inch mobile form factor, but the 3.5-inch Momentus XT desktop drives as well—it's all SSHDs starting this quarter. Anandtech has the most easily understandable chart for the new lineup, but the summary is that the 2.5-inch SSHDs come in 500GB and 1TB flavors and cost $79 and $99, respectively; the 3.5-inch SSHDs are available in 1TB and 2TB sizes and cost $99 and $149. All include 8GB of MLC NAND, which acts as a read and (apparently limited) write cache.

The pricing is a bit of a premium over non-SSHD disks, but Seagate claims that the performance benefits more than offset the cost. The 2.5-inch SSHD devices all spin their platters at 5400 RPM, but the 8GB of NAND should enable the disk to perform far better than a regular HDD on cache-friendly workloads (which generally include standard browsing and office-type work). One of the key measures of subjective computer speed is "snappiness," or how quickly the computer responds to user input; the key to the SSHD's success will be the accuracy and effectiveness of its caching algorithms and how smart the drive is about holding needed data in cache. A smart controller will mean better caching, which will mean less user input lag when opening applications or documents, which will mean a happier user.

Seagate's new drives are shipping as of today.

Lee Hutchinson
Lee is the Senior Technology Editor at Ars and oversees gadget, automotive, IT, and culture content. He also knows stuff about enterprise storage, security, and manned space flight. Lee is based in Houston, TX. Emaillee.hutchinson@arstechnica.com//Twitter@Lee_Ars

I like the Momentus XT 2.5. We bought a Mac mini with it's crappy 5krpm and swapped it for an XT. Awesome difference and you get another 250gb over the stock 500gb. Although the current 2.5 XT is 7200rpm, would be interested to see if there's a marked difference in performance. There should be better battery life however.

Now to benchmark the new drives. If it can outperform my 7200 rpm 2.5" drive significantly with zero to very minimal battery life hit, I'm game.

Just wish I could get at least a 768 gig SSD for a great price, which is around 300 bucks for me.

In all likelihood, it would improve battery life over a 7200 RPM drive.

1. solid state uses less power than spinning platter, and these drives want to maximize SSD use and minimize platter use2. 5400 RPM drives take less energy to spin than 7200 RPM drives (which is why for a while they were branded as ecodrives).

It might not be a lot of battery savings, but it definitely shouldn't make battery life worse.

Hmm. Has anyone done a teardown on the Chromebook Pixel? It's got a BIOS that's perfect for dual-booting (or even Hackintoshing), but that's more or less a non-starter with 32GB on board. Swapping in 1 TB of hybrid storage for $100 is appealing, but only if the Pixel has a 2.5" drive on-board.

Now to benchmark the new drives. If it can outperform my 7200 rpm 2.5" drive significantly with zero to very minimal battery life hit, I'm game.

Just wish I could get at least a 768 gig SSD for a great price, which is around 300 bucks for me.

In all likelihood, it would improve battery life over a 7200 RPM drive.

1. solid state uses less power than spinning platter, and these drives want to maximize SSD use and minimize platter use2. 5400 RPM drives take less energy to spin than 7200 RPM drives (which is why for a while they were branded as ecodrives).

It might not be a lot of battery savings, but it definitely shouldn't make battery life worse.

Now to benchmark them and compare to their top of the line 7200 rpm drives.

8GB is hardly very much for cache. If they were just going to stick with 8GB they could at least offset it by using SLC NAND so it can read and write to it much more often without as much of the loss of NAND life like in MLC or especially TLC.

8GB is hardly very much for cache. If they were just going to stick with 8GB they could at least offset it by using SLC NAND so it can read and write to it much more often without as much of the loss of NAND life like in MLC or especially TLC.

Well they are using SLC NAND (at least they did) and 8GB is a lot especially when you are running OSX or if you don't restart often... Got a Momentus XT 750GB SSHD with 8GB cache and the results are just amazing...

16GB of RAM costs around $120. With a decent amount of RAM like this I find the difference between a spinning disk and solid state to be start time. The second time application, configuration or all but the largest data files get used they are cached in RAM faster than any kind of drive. It is boot and first use reads where the SSD shows its stuff. I rarely find myself waiting on writes as modern file systems are good at caching and ordering.

SSDs are a pleasure for first use performance, spinning disks for capacity. Do you really want to micro manage which drive things go on? You know Windows will fight you at every turn dumping it all on C: any time your vigilance slips.

Used with a decent amount of RAM drives with a small amount of flash cache could give the first use performance of solid state combined with the large capacity of spinning disk. They could be very attractive. Time will tell, when we see real prices and real performance.

Hmm. Has anyone done a teardown on the Chromebook Pixel? It's got a BIOS that's perfect for dual-booting (or even Hackintoshing), but that's more or less a non-starter with 32GB on board. Swapping in 1 TB of hybrid storage for $100 is appealing, but only if the Pixel has a 2.5" drive on-board.

Being 32GB, I've no doubt that it's either soldered directly to the board or an Apple-like stick thing that slots in. A 2.5" drive to hold just 32GB storage would be incredibly wasteful on space.

I'm wondering if it would be possible for Seagate to come up with a custom firmware which would mimic operation of the Apple Fusion setup, while all being transparent to the user AND OS agnostic. That would be a very worthwhile drive to have as it would sit in a single drive-space while combining the large storage with fast SSD access.

One thing these hybrid drives will not do is fix power use in a laptop. A few times with Windows 7 I went full detective mode trying to get my laptop to quit hammering the hard drive while I was doing nothing but reading a long PDF on screen. There are a dozen svchost processes each hiding or housing a dozen service programs inside many of which just have to go on pounding the disk. There is an index for a search tool I never use and had to beg Google to teach me how to kill. There are perpetual update checks For all I know there is an auto search for child porn. After scrubbing all the crapware I could, Redmond and third party, I still had a busy hard drive while doing nothing.

Spinning disks will never compare on power use. I think it means a true portable laptop routinely used on battery should use an SSD and live with the capacity limits. USB3 and an external 2 1/2" drive can cover a lot.

SSDs are a pleasure for first use performance, spinning disks for capacity. Do you really want to micro manage which drive things go on? You know Windows will fight you at every turn dumping it all on C: any time your vigilance slips.

I find it a bit amazing that we are still talking about this particular problem in 2013.

16GB of RAM costs around $120. With a decent amount of RAM like this I find the difference between a spinning disk and solid state to be start time. The second time application, configuration or all but the largest data files get used they are cached in RAM faster than any kind of drive. It is boot and first use reads where the SSD shows its stuff. I rarely find myself waiting on writes as modern file systems are good at caching and ordering.

SSDs are a pleasure for first use performance, spinning disks for capacity. Do you really want to micro manage which drive things go on? You know Windows will fight you at every turn dumping it all on C: any time your vigilance slips.

Used with a decent amount of RAM drives with a small amount of flash cache could give the first use performance of solid state combined with the large capacity of spinning disk. They could be very attractive. Time will tell, when we see real prices and real performance.

ZFS is good at using SSDs for a cache.There were some case studies showing a ZFS RAID of 5400rpm SATA drives plus some SSDs for cache, keeping up with a RAID of 15krpm SAS drives in random or sequential. And the 5400rpm drives were much cheaper to purchase and even cheaper to run and more storage to boot.

edit: I think I misrepresented the "random" access. It was pseudo-random in that it was on a work load with lots of random aggregated requests, so not a true "random across the entire disk" kind of random.

ZFS is good at using SSDs for a cache.There were some case studies showing a ZFS RAID of 5400rpm SATA drives plus some SSDs for cache, keeping up with a RAID of 15krpm SAS drives in random or sequential. And the 5400rpm drives were much cheaper to purchase and even cheaper to run and more storage to boot.

I use a lot of Linux lately and of course still a significant amount of Windows, no ZFS on either. Obviously the job can be done creating a single file system across multiple devices. As you say ZFS does it and I believe there are dedicated external storage units for the server market which do this as well, perhaps using ZFS inside.

I would rather not do this ad hoc inside a PC. It would make the whole file system more fragile depending on the configuration and correct operation of two components instead of just one. Make that three components as it is two drives and the software which bind them together.

The Momentus XT lineup is pretty awesome. It only helps with read speeds, but that is where the performance matters most. I would like to see more NAND added as well as some tricks to make writing to the disc faster also.

Gaming is awesome on these things, but converting video is only half as awesome. Having increased write speeds will greatly impact the performance during video conversions.

Maybe they can use some of the NAND to hold onto data that needs to be written to the disc. Then the cache casually dumps the data onto the drive while it continues to do other things. This way the drive can continue to be read without having to worry about writes. The write can happen in between reads. Of course, this introduces the possibility of lost data in case something happens in-between writes. You don't want to falsely give the impression to the user of a successful write if it didn't happen that way. They just have to be smart with the implementation to handle data retention in case of minor hardware failure (where reboot fixes issues).

So what happens if you pair one of these things with a normal SSD to make an Apple Fusion Drive?

Does the world implode? Yo dawg i herd you like ssds so I put a ssd inside your ssd?

/can't be bothered to do a proper gif

I can't think of anything bad that would result. I don't think there is any distinct advantage to doing so either though. But if you had a hybrid, and decided to add a separate SSD as an upgrade I can't think of any reason that you would need to take the hybrid out...

So it drops spindle speed down to 5400RPM, and switches from SLC to MLC NAND? Apart from aerial density it seems like a non-upgrade. I hope they update the second gen 750 with the new write caching firmware the third gen has though, they promised that a looong time ago but never delivered, hopefully they do so now. Seems like there is no reason not to apart from greed, the NAND is the same capacity and a better type on the old one.

16GB of RAM costs around $120. With a decent amount of RAM like this I find the difference between a spinning disk and solid state to be start time. The second time application, configuration or all but the largest data files get used they are cached in RAM faster than any kind of drive. It is boot and first use reads where the SSD shows its stuff. I rarely find myself waiting on writes as modern file systems are good at caching and ordering.

SSDs are a pleasure for first use performance, spinning disks for capacity. Do you really want to micro manage which drive things go on? You know Windows will fight you at every turn dumping it all on C: any time your vigilance slips.

Used with a decent amount of RAM drives with a small amount of flash cache could give the first use performance of solid state combined with the large capacity of spinning disk. They could be very attractive. Time will tell, when we see real prices and real performance.

I agree. When I read about SSHDs, I though "wow"! Someone to make a drive in one casing, that presents itself as a 128GB SSD and 750GB HDD! But this 8GB flash cache concept is totally disappointing. It's better to buy an additional 8GB RAM stick, and probably actually cheaper than SSHD price premium.

For optimum performance you want SSD. For storage and longevity you want HDD. Currently you have to stuff laptops with both types of drives. If they made a hybrid - so that you could put your OS on SSD part and documents on HDD part - that would be AWESOME!

Gaming is awesome on these things, but converting video is only half as awesome. Having increased write speeds will greatly impact the performance during video conversions.

Do you really get held up waiting on disk writes for video conversion? The only place I hit a bottle neck on writes is software updates where frequent hard syncs are done to make sure the computer is never left in a broken state. For bulk writes I see anywhere from 60MB/sec to 160MB/sec where the smaller number comes from the slow part of a 2.5" drive. What video conversion I have done has been 100% CPU bound despite running on a 6 core Sandy Bridge. If 60MB/sec is too slow you probably need a lot of capacity as well as speed.

Gaming is awesome on these things, but converting video is only half as awesome. Having increased write speeds will greatly impact the performance during video conversions.

Do you really get held up waiting on disk writes for video conversion? The only place I hit a bottle neck on writes is software updates where frequent hard syncs are done to make sure the computer is never left in a broken state. For bulk writes I see anywhere from 60MB/sec to 160MB/sec where the smaller number comes from the slow part of a 2.5" drive. What video conversion I have done has been 100% CPU bound despite running on a 6 core Sandy Bridge. If 60MB/sec is too slow you probably need a lot of capacity as well as speed.

This is an anecdote and all that, but I can stream 3 1080p BluRay raw streams off of a large 5400RPM drive.

I cannot imagine how any type of video conversion would need more than that unless you need more streams or 4k/8k. The video people I work with 8k source media files need more than that, but they dealing with lossless video on top of the higher resolution. (Though 99.9% of them time they are dealing with 24fps except for effects which are sometimes @ 60fps/30fps.)

As an owner of the (2nd gen) 750GB Momentus XT in my desktop after being bitten once too many by Western Digital quality problems lately, I was really looking to the SSHD updates that they were talking about at CES for the spring. Besides the forthcoming desktop updates they spoke of (double capacity), I figured that they would bump the cache to 32GB and have more density that should be expected for a year later.

But seriously, the only way to spin this release is they went cheap, cheap, cheap.

7200 down to 5400. Tiny bumps in size and most perplexing the flash size is left at 8GB and that is after the benefits they got by switching to MLC.

Unless they are planning on announcing some better drives soon, perhaps I have to wait for the promised WD Black drives after all.

For optimum performance you want SSD. For storage and longevity you want HDD. Currently you have to stuff laptops with both types of drives. If they made a hybrid - so that you could put your OS on SSD part and documents on HDD part - that would be AWESOME!

That is pretty much what they've done, you just don't get to see them (or worry about them) as two separate drives. The caching algorithms make sure stuff you use often is in the cache, which is what you're asking for. Though 8Gb is maybe a bit small, you'd probably want 32Gb+ to work really well.

I'm glad they are expanding the hybrid options. Their XT drives are wonderful for upgrades to older laptops, giving them a second life without limiting capacity.

I do not understand why they are limiting to 8 GB, though. Why can't they sell the same model as 2-3 cach sizes of varying price. Like 8 GB, 16 GB and 32 GB options for a 1TB spinning drive. Is it really that much trouble for them to design more than one controller board?

As always, amazed at how easily fanboys get their brands into the discussion above and get uprated to boot.

I continue to not understand why they don't make these things behave like hybrid hard drives, as supported by Windows ReadyDrive.

Granted that this would only work for Windows and not Mac OSX or Linux, but the drive could easily figure out if the OS was using the new stuff in SATA that supports HHDs, and if not, use Seagate's onboard firmware to run the cache.

I agree. When I read about SSHDs, I though "wow"! Someone to make a drive in one casing, that presents itself as a 128GB SSD and 750GB HDD! But this 8GB flash cache concept is totally disappointing. It's better to buy an additional 8GB RAM stick, and probably actually cheaper than SSHD price premium.

Additional RAM doesn't help with startup or (usually) loading programs. The 8GB cache does. It's nice that it's transparent to the user, too. Would I like a bigger cache? Sure. And for a laptop I can see a function to a device that presents as two separate drives, one SSD and one HD. But the hybrid drive does work pretty well.

I agree. When I read about SSHDs, I though "wow"! Someone to make a drive in one casing, that presents itself as a 128GB SSD and 750GB HDD! But this 8GB flash cache concept is totally disappointing. It's better to buy an additional 8GB RAM stick, and probably actually cheaper than SSHD price premium.

Additional RAM doesn't help with startup or (usually) loading programs. The 8GB cache does. It's nice that it's transparent to the user, too. Would I like a bigger cache? Sure. And for a laptop I can see a function to a device that presents as two separate drives, one SSD and one HD. But the hybrid drive does work pretty well.

How's it different if 8 GB cache is in NAND or DRAM? 8 GB is too small to help you with starting anything (for the first time). But DRAM is much much faster than NAND via SATA.

I agree. When I read about SSHDs, I though "wow"! Someone to make a drive in one casing, that presents itself as a 128GB SSD and 750GB HDD! But this 8GB flash cache concept is totally disappointing. It's better to buy an additional 8GB RAM stick, and probably actually cheaper than SSHD price premium.

Additional RAM doesn't help with startup or (usually) loading programs. The 8GB cache does. It's nice that it's transparent to the user, too. Would I like a bigger cache? Sure. And for a laptop I can see a function to a device that presents as two separate drives, one SSD and one HD. But the hybrid drive does work pretty well.

How's it different if 8 GB cache is in NAND or DRAM? 8 GB is too small to help you with starting anything (for the first time). But DRAM is much much faster than NAND via SATA.

NAND cache can survive power cycles, so it can speed up bootstrap and image startup time even after the machine has been powered off.

As for "8 GB is too small", Seagate's algorithm (and Windows' ReadyDrive for that matter) only caches the results of short random reads. The goal is to minimize the impact of a bunch of little reads that are happening around the same time as some long sequential reads (where even an SSD doesn't help that much). And it works ok, even with only 8 GB flash.

Per reports though, Seagate doesn't cache anything that's read after the first minute after power-up (or maybe a reset). Which means it will only optimize booting, not app startup later. And, really... how often do you boot your machine?

So what happens if you pair one of these things with a normal SSD to make an Apple Fusion Drive?

Does the world implode?

No, but it may be a big waste of time. As outline either in this or Anandtech article the Seagate caching algorithm is heavily skewed toward catching data related to the first couple of minutes of startup. Well in a fusion set up the vast majority of that will have already been cached on the SSD if you boot start the computer every day.

I wonder the algorithm is caching off of each power-up from sleep probably also. Again there may not be much going on if the Fusion/CoreStorage SSD has already cached the majority of that. Two major problems. Since the SSHD doesn't see all of the data, it doesn't get lots of info. Second, its So you'd end up with 8GB of Flash not being used much as all.

caching algorithm is not as "smart" as Apple's. Fusion needs "pause and think time" while you stop accessing the disk for a while but it doesn't "go to sleep on the job" several minutes after the power turns on either.

I do not understand why they are limiting to 8 GB, though. Why can't they sell the same model as 2-3 cach sizes of varying price. Like 8 GB, 16 GB and 32 GB options for a 1TB spinning drive. Is it really that much trouble for them to design more than one controller board?

Combintorical explosion of products.

3 caches x 3 HDD = 9 products.

Are there really 9 different submarkets here of are large enough for scale. Two major problems.

1. The problem is how many of each do you make if they really are that extremely well differentiated markets

2. The difference is negligible. 8 GB is less than 1% of 1 TB. 16 GB barely 2% . 32 GB barely 3% There are not radical caching performance differences for those kinds of changes. Going from 0.01% to 1% yes? From 1% to 8% maybe. From 1% to 10% probably. Nickel and diming on single digit percentages? Not really.

If there is it is more likely something very wrong with the overall caching heuristics/algorithm than on size.

As to why it is so small? Because there 2.5" or 3.5" drive is still inside the container. Where they fit the Flash chips is in the "extra space". There is no room for 4-5 flash chips. So restricted to single chip packages (maybe two). The cost also goes up also.

The advantage that SSHD has over SSD is still capacity; not trying to be "as fast as SSD". The goal is to be faster than a plain HDD without sacrificing capacity at all. For average workloads, they typically they are.

They probably went from SLC to MLC because the heuristics are more highly selective of what is cached and the controllers being used can deal with it. Also seems likely that is usable caching storage as opposed to the 'raw total' amount of flash present. Over-provisioned 50% there could be 16GB total there and only 8GB usable.

2. 5400 RPM drives take less energy to spin than 7200 RPM drives (which is why for a while they were branded as ecodrives).

It might not be a lot of battery savings, but it definitely shouldn't make battery life worse.

Both the new 1 TB 5400 rpm "SSHD" drive and the old 750 GB 7200 rpm Momentus XT say "5V 0.70 A" on their label. So it's tough to see how the new drive is going to save any power. It'll just be slower and have larger capacity.

I am wondering how these drives will do in a "storage spaces" situation, or using a RAID with LVM. I am right now researching these options (including ZFS) for updating my media server so I don't have to big a worry about lost media files. I particularly like ZFS but it isn't an easy solution for those who don't normally dabble in Linux. Basically I am leaning toward a parity based storage solution, hence the ones I mentioned. But how will the algorithm of these drives work with those file systems, setups?

PS and one of the things I really liked about storage spaces in win8 is the lack of need to have similar sized HDD's to do the "storage volume".